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Federal Aviation Administration, DOT 

§ 171.259 

§ 171.255

Requests for IFR procedures. 

(a) Each person who requests an IFR 

procedure based on an ISMLS facility 
that he owns must submit the fol-
lowing information with that request: 

(1) A description of the facility and 

evidence that the equipment meets the 
performance requirements of §§ 171.259, 
171.261, 171.263, 171.265, 171.267, and 
171.269, and is installed in accordance 
with § 171.271. 

(2) A proposed procedure for oper-

ating the facility. 

(3) A proposed maintenance organiza-

tion and a maintenance manual that 
meets the requirements of § 171.273. 

(4) A statement of intent to meet the 

requirements of this subpart. 

(5) A showing that the ISMLS facil-

ity has an acceptable level of oper-
ational reliability, maintainability and 
acceptable standard of performance. 
Previous equivalent operational experi-
ence with a facility with identical de-
sign and operational characteristics 
will be considered in showing compli-
ance with this paragraph. 

(b) After the FAA inspects and evalu-

ates the ISMLS facility, it advises the 
owner of the results and of any re-
quired changes in the ISMLS facility 
or in the maintenance manual or main-
tenance organization. The owner must 
then correct the deficiencies, if any, 
and operate the ISMLS facility for an 
inservice evaluation by the FAA. 

§ 171.257

Minimum requirements for 


(a) The following are the minimum 

requirements that must be met before 
the FAA approves an IFR procedure for 
a non-Federal ISMLS facility: 

(1) The performance of the ISMLS fa-

cility, as determined by flight and 
ground inspection conducted by the 
FAA, must meet the requirements of 
§§ 171.259, 171.261, 171.263, 171.265, 171.267, 
and 171.269. 

(2) The installation of the equipment 

must meet the requirements of 
§ 171.271. 

(3) The owner must agree to operate 

and maintain the ISMLS facility in ac-
cordance with § 171.273. 

(4) The owner must agree to furnish 

periodic reports as set forth in § 171.275 
and agree to allow the FAA to inspect 

the facility and its operation whenever 

(5) The owner must assure the FAA 

that he will not withdraw the ISMLS 
facility from service without the per-
mission of the FAA. 

(6) The owner must bear all costs of 

meeting the requirements of this sec-
tion and of any flight or ground inspec-
tion made before the ISMLS facility is 
commissioned, except that the FAA 
may bear certain costs subject to budg-
etary limitations and policy estab-
lished by the Administrator. 

(b) If the applicant for approval 

meets the requirements of paragraph 
(a) of this section, the FAA approves 
the ISMLS facility for use in an IFR 
procedure. The approval is withdrawn 
at any time that the ISMLS facility 
does not continue to meet those re-
quirements. In addition, the ISMLS fa-
cility may be de-commissioned when-
ever the frequency channel is needed 
for higher priority common system 

§ 171.259

Performance requirements: 


(a) The ISMLS consists of the fol-

lowing basic components: 

(1) C-Band (5000 MHz–5030 MHz) local-

izer equipment, associated monitor 
system, and remote indicator equip-

(2) C-Band (5220 MHz–5250 MHz) glide 

path equipment, associated monitor 
system, and remote indicator equip-

(3) VHF marker beacons (75 MHz), as-

sociated monitor systems, and remote 
indicator equipment. 

(4) An ISMLS airborne receiver or a 

VHF/UHF ILS receiver modified to be 
capable of receiving the ISMLS signals. 
This modification requires the addition 
of a C-Band antenna, a converter unit, 
a microwave/ILS mode control, and a 
VHF/UHF receiver modification kit. 

(b) The electronic ground equipments 

in paragraph (a)(1), (2), and (3) of this 
section, must be designed to operate on 
a nominal 120/240 volt, 60 Hz, 3-wire sin-
gle phase AC power source. 

(c) ISMLS ground equipment must 

meet the following service conditions: 

(1) AC line parameters, DC voltage, 

elevation, and duty: 

120 V nominal value, 102 V to 138 V (


1 V).* 

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